1. Field of the Invention
The present invention relates to an information processing apparatus that is connected to a network via a network interface device and is capable of performing encrypted communication with external apparatuses on the network, and a communication system including the network interface device and the information processing apparatus.
2. Description of the Related Art
Conventionally, there has been known an information processing system provided with an energy saving mode for reducing power consumption in a standby state. As one example of this type of information processing system, there has been proposed a communication system comprised of an information processing apparatus as a main unit which is provided with a main CPU, and a NIC (Network Interface Card) device provided with a sub CPU. In general, a communication system of the above-mentioned type is configured such that during the energy saving mode of the system, the information processing apparatus as the main unit is caused to shift to the energy saving mode, whereas the NIC device, which consumes a smaller amount of energy, is caused to remain on standby while causing power to be normally supplied to modules of the NIC device.
Further, Japanese Patent Laid-Open Publication No. 2006-259906 discloses a method in which immediately before the information processing apparatus as the main unit shifts to the energy saving mode in which power supply to a main CPU is stopped, the main CPU notifies the sub CPU of the address of a multicast packet to be responded to. This method enables the sub CPU to respond, on behalf of the main CPU, to multicast packets received in a state where power supply to the main CPU is stopped, so that it is possible to eliminate the need to start the main CPU. In short, this makes it possible to prolong the stoppage of power supply to the main CPU to thereby enhance the effect of energy saving.
By the way, in recent years, to protect secret information, IPSec (Internet Protocol Security), SSL (Secure Socket Layer) and the like have been proposed as techniques for performing communication by encrypting a network path. The use of these techniques makes it possible to transmit and receive data in an encrypted state over a network to thereby prevent leakage of information.
As described hereinabove, by storing information on packets to be responded to in the NIC device, the NIC device can respond to received packets on behalf of the main-unit information processing apparatus after it has shifted to the energy saving mode.
However, in a case where the NIC device is caused to respond to a packet on behalf of the information processing apparatus, if the packet received via the network is an encrypted one, the NIC device may not be able to properly respond to the packet.
More specifically, to cause the NIC device to respond to a packet on behalf of the information processing apparatus as the main unit, a pattern of a packet to be responded to and a packet to be transmitted as a response to a packet whose pattern matches the pattern are registered in the NIC device in advance. The NIC device having received a packet whose pattern matches the registered pattern transmits the registered packet which is associated with the pattern. At this time, however, in a case where the packet received by the NIC device is an encrypted one, even if the pattern of the packet actually matches the registered pattern, the NIC device determines, through comparison between a pattern of the encrypted packet and the registered pattern, that there is no match between the two.
In this case, it is required to return the information processing apparatus as the main unit from the energy saving mode to a normal power mode and then transfer the packet received by the NIC device to the information processing apparatus. Therefore, the number of times of returning the information processing apparatus as the main unit to the normal power mode increases, resulting in reduced energy saving effects.